To be honest, while I agree that there is some tat out there, all this hatred that is spouted for "Modern Bikes" is, in the most part, utter drivel!!!
Attention to detail? Please!
Look at the design and manufacturing that has gone into that SantaCrus sull suss above.... 20 years ago, full suss was at best, flexy, wobbly, unpredicatable and used straight pipes
Function over form? Please!
I would rather have something that does what it is designed to do, consistently, and relaiably, than to be at best OK, but look pretty (Wife?
Rose tinted blinkers
Don't get me wrong, I love the nostalgia for the age in which I grew up utterly obsessed by mountain bikes of that day, but this^.
Never forget that old-school Marins, Konas, Specializeds, Oranges, etc, were all mass-produced in the far east, just as they are today. Take away the paintjobs and most retro bikes from the early 90's are almost indistinguishable from each other except to true enthusiasts. Maybe a wishbone stay here or there, the style of dropouts, the cable routing... Get ten retro frames all kitted up with the same components and in a blind test you'd struggle to tell them apart.
Modern FS designs are, on the other hand, almost instantly identifiable, and have very different ride characteristics (I'm told) - FSR is very active but supportive, VPP such as Giant's Maestro tend to blow through midrange travel very quickly with a standard tune shock, single pivots suffer from brake jack, etc, etc...
There is far more scope for picking exactly the type of bike for the riding you do, whereas 20 years ago you could maybe choose 60mm of front suspension if you were lucky enough to be able to afford it.
Want a skinny-tubed steel frame? On-One, Cotic, Charge, Dialled Bikes, Sanderson and Pipedream all make them, and that's just UK companies. Hope are still making boutique machined hubs and brakes, and there's a myriad of US companies still producing gorgeous CNC stuff. You can still build a very retro-looking bike from brand new components if you want, and it will cost comparably what a boutique build would have back then. Just because it's not what the masses want (or think they want!), doesn't mean it's not out there...
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